There is a known endoscope that has an angle of view that is equal to or greater than 180°, and with which it is possible to simultaneously observe front, lateral, and rear viewing fields (for example, see Patent Literature 1). For example, in the case in which an endoscope having an angle of view that is equal to or greater than 180° is used in the colon, in which numerous folds are present, with the endoscope of Patent Literature 1, it is possible to observe the back side of a fold without greatly changing the direction in which the distal end of the endoscope points, and thus, manipulations by a user are facilitated, and it is possible to more reliably find a lesion. An illumination apparatus of this endoscope is capable of uniformly illuminating large lateral and front areas by diffusing, by means of a diffusion layer, illumination light guided by a light guide.